The invention relates to a method for identifying contamination and/or condensation on components of a voltage intermediate circuit converter.
In converters, in particular voltage intermediate circuit converters, operation where condensation or unacceptable contamination is present leads to flashover which damages or destroys the converter.
By means of a correspondingly robust design, for example by means of air gaps and creep gaps of a sufficient size and/or a high protection grade, attempts are made to reduce the sensitivity to operation in the presence of condensation and/or contamination. Operation where condensation and/or contamination is present is incorrect operation, which is normally not permitted. Instructions in documentation for the converter (operating instructions, commissioning instructions, handbook) are intended to ensure that a converter is only used in the correct manner. In other words, it is not possible for incorrect operation to take place.
When circumstances are present for a converter to be damaged or destroyed, it is assumed that the instructions for use have not been adhered to. In other words, the damaged or destroyed converter has not been used in the correct manner.
A method for detecting the degree of contamination on an operational converter device is known from DE 10 2004 018 578 B4. According to this method, a surface conductance of a part of the converter device which is subjected to the ambient air around the converter device is determined and compared with a predetermined limit value. This determined comparison value is a measurement of the degree of contamination on the converter device. By means of this method, even before the operation is interrupted, the risk is identified of protective shutdown of the converter device as a result of the contamination. Such contamination on the converter device occurs precisely when said converter device is not operated according to its protection grade.
A method for protecting a device to be cooled from condensation is disclosed in DE 10 2007 023 056 A1. According to this method, depending on a determined temperature of a cooling device of the device to be cooled, a determined coolant inlet temperature and a predetermined temperature of the air surrounding the device to be cooled, an adjusting signal is generated, by which the coolant volumetric flow is adjusted such that the temperature of the cooling device is the same as the ambient air. As a result, in the region of the cooling device a liquid phase of the air is prevented from being omitted and condensation is prevented from being able to be formed on devices to be cooled of said region of the cooling device. Thus protection against condensation is achieved.
These known methods are implemented during operation of a converter, in particular a voltage intermediate circuit converter. As a result, these known methods are not able to protect a converter, which is intended to be operated again after a lengthy stoppage time, from flashover which results from condensation and/or unacceptable contamination.
The object of the invention, therefore, is to provide a method by which at least during a pre-charging process of an intermediate circuit capacitor of a voltage intermediate circuit converter the degree of contamination and/or condensation may be identified.